In the past, it was accepted that .beta.-adrenaline receptors are classified into two groups .beta.1 and .beta.2, wherein the stimulation by .beta.1 induces an increase in the cardiac rate and the stimulation by .beta.2 brings about relaxation in the smooth muscle tissue and lowering of blood pressure. Arch et al discovered a compound which exhibits scarce activities to .beta.1 and .beta.2 but emphasizes lipolysis of fatty cells, wherefrom they have made clear the existence of a third receptor [Nature, 309, 163-165 (1984)]. Afterwards, the primary structure thereof was clarified [Emorine et al: Science, Vol. 245, 1118-1121 (1989)] and the receptor was named as .beta.3.
Recently, it has been shown that compounds exhibiting a .beta.3-activity are useful as a drug for preventive treatment of diabetes, obesity, hyperlipemia, digestive diseases and depression [Int. J. Obesity 8 (suppl. 1), 93-102 (1984); Nature, 309, 163-165(1984); U.S. Pat. No. 5,120,766; Brit. J. Pharmacol.,103, 1351-1356 (1991); Eur. J. Pharmacol., 219, 193-201 (1992)].
Various compounds with correlation to .beta.3 have been reported in the literatures, for example, a compound (BRL 37344) having the following molecular structure ##STR1## as disclosed in EP 023 385 and in Drugs of the Future, Vol. 16, 797-800 (1991); a compound (CL316, 243) having the following molecular structure ##STR2## as disclosed in EP 0 455 006 and J. Med. Chem., Vol. 35, 3081-3084 (1992); a compound having the following molecular structure ##STR3## as disclosed in W09429290; and a compound having the following molecular structure ##STR4## as disclosed in EP 0 659 737 in Example 1 thereof. All these compounds have molecular structures different clearly from that of the compound according to the present invention.
There was known a compound exhibiting a function for increasing the myocardial contraction strength and for antagonizing obesity represented by the following structural formula ##STR5## as disclosed in EP 171 702, which is distinguished from the compound according to the present invention in that it has a strong pharmacological activity onto the heart and has a molecular structure quite different from that of the compound according to the present invention.
Further, a compound exhibiting an .alpha.,.beta.-blocking activity, namely, a function of lowering the blood pressure, represented by the following structural formula ##STR6## is disclosed in Japanese Patent Kokais Sho 55-53262 and Sho 58-41860 and a compound exhibiting a vasodilatoric function represented by the following structural formula ##STR7## is disclosed in DE 2 651 572. They are different from the compound according to the present invention in the molecular structure and in function.
There is a demand for a novel and effective medicament or pharmaceutic composition which can be used for therapuetic treatment and preventive treatment of diseases correlating to .beta.3, such as diabetes, obesity and hyperlipemia.